P0448 on 2017-2019 Infiniti Q60: EVAP Vent Valve and ECM Fixes

What's Unique About the 2017-2019 Infiniti Q60

What makes the 2017-2019 Infiniti Q60 unique regarding P0448 is the high likelihood of a software problem compounding the diagnosis. Infiniti released several Technical Service Bulletins (TSBs), including ITB19-012a and ITB19-027a, because the Engine Control Module (ECM) was prone to incorrectly storing a permanent P0448 code due to calibration errors. Crucially, the TSB clarifies that the reprogram does not fix the underlying cause of the code but rather updates the ECM logic so the permanent DTC can be erased after the actual hardware repair (e.g., replacing the valve or fixing wiring) is completed. This means the first step is to diagnose and repair the hardware fault, and the final step is the dealer reprogram to clear the permanent code.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle. 👇

Symptoms You May Notice

• Check Engine Light is on
• Failure to pass an emissions inspection
• Possible faint fuel smell near the rear of the vehicle.
• Difficulty refueling (gas pump nozzle clicks off repeatedly) 🎬 See this video for a clear explanation of the P0448 code. if the valve is stuck closed.

Most Likely Causes

1. Engine Control Module (ECM) Software Calibration Error 🔴 High Probability → Shop Engine Control Module (ECM) Infiniti issued multiple TSBs (ITB19-012a, ITB19-027a, P9329) confirming that the ECM can improperly store a permanent P0448 code due to software errors, preventing it from being cleared with a standard OBD-II scanner.
   How to confirm: An Infiniti dealer must check the current ECM part number against the numbers listed in the TSBs. If the code persists after a hardware fix, the reprogram is necessary.
   Typical fix: Reprogramming the ECM with updated software. This must be done by a dealer using a CONSULT-III plus tool after the root cause has been repaired.
   Est. part cost: $0 - $200 (if not covered under a campaign)
2. Failed EVAP Canister Vent Control Valve 🟡 Medium Probability → Shop Vapor Canister Vent Valve The valve's solenoid can fail electrically (short circuit) or mechanically (get stuck) over time due to heat, moisture, and age. It is a common failure point across many Nissan and Infiniti models.
   How to confirm: Test the valve's operation by applying 12V power to see if it actuates 🎬 Watch: How to test and replace the vent control valve. (clicks and closes). Check for resistance across the terminals with a multimeter. A functioning valve should click when power is applied.
   Typical fix: Replace the EVAP canister vent control valve. It is located on the charcoal canister, behind the driver's side rear wheel.
   Est. part cost: $40-$120
3. Wiring Harness or Connector Issue ⚪ Low Probability The wiring harness leading to the vent valve is located under the vehicle and is exposed to road debris and moisture, which can cause corrosion or physical damage leading to a short circuit. One owner reported unusual voltage readings (13V and 3V) at the connector, pointing to a circuit issue rather than a failed valve.
   How to confirm: Visually inspect the wiring and connector for any signs of damage, fraying, or corrosion. Use a multimeter to check for correct voltage (should be ~12V and a ground) at the connector with the ignition on.
   Typical fix: Repair the damaged section of the wiring harness or replace the connector.
   Est. part cost: $10-$50

Rare But Worth Checking

• Failed EVAP Charcoal Canister: → Shop Vapor Canister The canister can become saturated with fuel or water, or crack, which can affect the entire EVAP system and sometimes damage the vent valve. In some cases, the port where the valve mounts can become clogged with dirt or debris, causing a restriction.
• Faulty Engine Control Module (ECM): → Shop Engine Control Module (ECM) In very rare cases, the driver circuit within the ECM that controls the vent valve can fail. This is a last resort diagnosis and should only be considered after all other possibilities, including the software update, have been exhausted. A replacement ECM is very expensive.

Diagnosis Steps

1. Scan for Codes: Confirm P0448 is the only code present. If other EVAP codes are stored, their diagnosis may need to be prioritized.
2. Check for Technical Service Bulletins (TSBs): Be aware that TSBs ITB19-012a, ITB19-027a, or P9329_P9344_P934 exist. Understand that an ECM reprogram will likely be the *final* step to clear the code after a hardware fix.
3. Locate and Inspect the Vent Valve: The valve is mounted on the charcoal canister, accessible from behind the driver's side rear wheel. Visually inspect the valve, its connector, and the nearby wiring for obvious damage, corrosion, or loose connections.
4. Test the Vent Control Valve: Disconnect the valve and test its solenoid. Briefly apply a 12V power source to its two terminals; a healthy valve will produce an audible 'click' as it closes. You can also check the resistance with a multimeter to see if it's within the manufacturer's specification (a specific ohm range may be available in the factory service manual).
5. Check for Power at the Connector: With the ignition on, use a multimeter to verify that the harness connector is receiving power (~12V) and has a good ground. A Q60 owner experiencing this issue reported abnormal readings of 13V and 3V, indicating a wiring fault.
🎬 Watch: A helpful guide to fixing EVAP vent circuit issues.
6. Inspect the Charcoal Canister and Port: When the valve is removed, inspect the port on the canister for any dirt, dust, or carbon blockages that could impede airflow or prevent the valve from seating correctly.
7. Perform Repair and Reprogram: If the valve is faulty, replace it. If the wiring is damaged, repair it. Afterwards, if the Check Engine Light cannot be cleared, the vehicle must be taken to an Infiniti dealer for the ECM reprogram as outlined in the TSBs.

Parts You'll Likely Need

• EVAP Vapor Canister Vent Solenoid Valve (OEM #14935-JF00B (or superseded numbers 14935-JF00E, 14935-JF01C)) — This is the component that fails most often if the issue is not software-related. It contains the solenoid that can short out or get stuck. The part number has been updated several times; 14935-JF01C is one of the latest versions.
  Trusted brands: Infiniti (OEM), Bosch, Dorman (911-504), TRQ
  OEM price range: $90-$150
  Aftermarket price range: $40-$80

Technical Service Bulletins (TSBs) & Recalls

• ITB19-012a: MIL ON WITH DTC P0448
• ITB19-027a: MIL ON WITH DTC P0087, P0101, P0448, OR P2008, VEHICLES REGISTERED OUTSIDE OF CALIFORNIA
• P9329_P9344_P934: California-specific campaign to reprogram the ECM for improperly stored P-DTCs including P0448.
• ITB19-027: MIL ON WITH DTC P0087, P0101, P0448, OR P2008

Platform-Specific Known Issues

• Infiniti identified a calibration error in the ECM that could cause a permanent diagnostic trouble code (P-DTC) for P0448 to be stored incorrectly. This is documented in TSB #P9329_P9344_P934 for vehicles in California.
• TSB #ITB19-027a and #ITB19-012a also address the MIL being on with DTC P0448, pointing to an ECM reprogram as the solution for certain vehicles.
• The EVAP vent valve is located on the charcoal canister, which is found behind the rear driver's side wheel well.

Mechanic-Grade Diagnostic Values

• EVAP Canister Vent Control Valve Solenoid Resistance — expected: 20 - 50 Ohms. Failure: A reading outside this range, or an open/infinite reading, indicates a failed solenoid coil.
• Voltage at Vent Valve Connector (Ignition ON, Engine OFF) — expected: One pin should have ~12V (battery voltage), the other is the ground controlled by the ECM.. Failure: No voltage suggests a blown fuse or wiring issue. Abnormal voltage on the ground pin (e.g., 3V as reported by one owner) suggests a short or a problem with the ECM driver circuit.

Scan Tool Commands That Help

• Infiniti CONSULT-III plus: EVAP System Leak Check (Active Test) — This function commands the vent valve to close, sealing the system. The technician can then monitor the fuel tank pressure sensor to check for leaks or verify a repair without a smoke machine.
• Infiniti CONSULT-III plus: Erase All DTCs — This is a required final step after an ECM reprogram. The specific procedure involves turning the ignition off, then on, and waiting for the erase to complete to ensure permanent codes are cleared.
• Bidirectional Scan Tool (General): EVAP Vent Solenoid On/Off — Allows a technician to manually command the vent valve to open and close to test its mechanical function (listening for a click) and the integrity of the control circuit.

Wiring & Ground Locations

• EVAP Canister Vent Control Valve Connector — On the EVAP canister, located behind the rear driver's side wheel well liner.. This is the primary point for electrical testing. A Q60 owner identified the wires as Brown and Green. Checking for voltage, ground, and corrosion here is a critical diagnostic step.
• Engine Control Module (ECM) — Under the dashboard, typically on the passenger side for this platform.. The ECM provides the switched ground signal that activates the vent valve. A wiring fault between this module and the valve, or a failure of the ECM's internal driver circuit (rare), can cause P0448.
• Fuse/Relay Box (Interior) — Under the instrument panel on the driver's side, behind a cover on the pillar.. Contains fuses for various body and control modules. While a specific EVAP fuse isn't always labeled, a fault in a related circuit could originate here.
• Fuse/Relay Box (Engine Compartment) — Located in the rear of the engine bay, near the battery. There can be multiple boxes.. This box houses main power distribution fuses and relays. The power feed for the EVAP vent valve circuit likely originates from or passes through this area.

Real Owner Repair Stories

• Reddit user in r/infiniti (2018 Infiniti Q60S) — Check Engine Light with code P0448.
  ❌ Tried (didn't work) Took it to the dealership, who could not figure it out and suggested it might be the gas cap., Manually tested the vent control valve with a 12V battery; confirmed it clicked closed correctly., Visually inspected wiring harness for damage.
  ✅ What actually fixed it The user did not post a final fix, but their detailed diagnosis revealed abnormal voltage at the valve connector (13V on the power wire, 3V on the ground-side wire with the engine running). This strongly pointed to a wiring issue (short to power on the ground side) or a faulty ECM driver, rather than a failed valve. This is a critical finding for others who have already tested or replaced the valve itself.

OEM Part Supersession History

• 14935-JF00A / 14935-AM60B → 14935-JF00B -> 14935-JF00C -> 14935-JF00E -> 14935-JF02C — Standard part evolution for improved reliability and material changes.
  Heads up: While many of these parts are physically interchangeable across various Nissan/Infiniti models, it is critical to use a part number specified for the VR30DDTT platform. Using a valve from an older VQ-series engine may result in incorrect operation even if it fits.